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Posted: Jun 21, 2011

Talking about nanotechnology's unimagined possibilities

(Nanowerk News) The term "nanotechnology" covers a multitude of different technologies, and so a differentiated view of it is needed. This is the opinion of ETH Zurich Professor Christofer Hierold, whose research is in nanotechnology. He says that, to avoid risks and hazards, these must be analysed for each specific example of materials, structures and their applications.

Christofer Hierold is Professor of Micro and Nanosystems at ETH Zurich and, together with Adrian Ionescu, Professor at EPF Lausanne, he is coordinator of the "Guardian Angels" project, which has applied for an EU flagship project. (Photo: Philippe Neidhart/ETH Zurich)

Prof. Hierold, what would the world look like without nanotechnology?

That is certainly an interesting question. For a long time now, nanotechnologies have been used in the products and fabrication technologies that we still describe with the term microelectronics. For example, the tiniest structures in integrated transistors are in the range of a few tens of nanometres. Without the nanotechnology used to manufacture these components, we would not have these products of modern IT technologies. We would also have no efficient surface technologies with their dirt-repellent or antibacterial effects, and no concepts for dietary supplements that enable the body to absorb trace elements efficiently. We would lack all these good examples that are lumped together under the generic term "nanotechnology".

In other words, we in our heavily technologised world would be facing something of a setback?

Mentioning nanotechnology more or less opens up a zoo of very different topics. When we say we would be set back by decades, we must define exactly what we mean here. By using nanotechnology and its options for miniaturisation, we have put ourselves on a development path that has permitted considerable efficiency savings in terms of costs, energy and resources. This development would not have occurred without nanotechnological processes. However, nanostructures have also allowed us to create materials with new functionalities, e.g. good electronic properties, good optical properties or the surface properties mentioned earlier. You can add to that the catalytic properties of nanoparticles or the improved materials properties in composites.

Do we have the technology firmly under control, or are we leaving problems for succeeding generations?

We must study the risks of the various nanomaterials, i.e. the probability of being exposed to them directly and their dangers. Of course researchers must also consider the effect of nanomaterials on the environment, insofar as they can enter the environment during the life cycle of a product.

In other words....

….Nanoparticles are mostly incorporated into other materials or applied to their surface, e.g. silver particles in wall paints. It is known that these silver particles wash out and reappear in sewage works. The good news is that they no longer occur there as tiny nanoparticles but as larger agglomerated particles. You need to clearly distinguish the configuration in which these materials are used. This is why I dislike generalisations.. It really is necessary to consider every material individually and study and assess every form of the material according to its size and shape, and then take appropriate precautions.

ETH Zurich is involved in risk assessment, either through research projects or by setting up a precautionary matrix for synthetic nanomaterials. What else needs attention?

In my opinion, there are two aspects to the precautionary matrix. It enables a criteria-based assessment of the materials while at the same time making us aware that using new materials can entail certain risks. However, setting up the matrix and the discussion surrounding the risks of nanomaterials have also shown that no new rules for handling nanomaterials are needed. Although the existing regulations are sufficient, every new material still needs to be assessed appropriately. If there is any doubt, it is classified as toxic, i.e. dangerous, as happened with carbon nanotubes. For our laboratory work, it is important that our students and staff are trained in handling nanomaterials. At the same time, we also draw a distinction depending on whether we can come into contact with nanoparticles directly, e.g. by inhalation, or whether they only occur in solution or bonded to surfaces. If nanoparticles or carbon nanotubes are present for example as individual electronic components in sensors, as in our case, then they are firmly bonded to the component and are protected by a package, so the risk they pose is very small.

Your research group works with carbon nanotubes, whose effect is often compared to asbestos. How dangerous are they really?

It is known from studies that carbon nanotubes of certain lengths can cause inflammatory responses at the cellular level. Researchers believe the aspect ratio, i.e. the relationship between the length and diameter of the nanostructures, to be important for such reactions. Other studies are however focusing on the ability of nanotubes to penetrate through the cell membrane, enabling them to act as transporters for medicines, maybe even such as to combat tumour cells. At present, we still know too little to be able to evaluate and assess correctly the interactions between carbon nanotubes and living materials. As long as the activity correlations remain unclarified, we must regard this material as hazardous, especially in the laboratory when we prepare this material and work with it.

You stress that "one must be careful when handling carbon nanotubes". How do you train your scientists to do this?

We have introduced safety rules for handling carbon nanotubes in our laboratory. When working at the open reactor in which we manufacture the nanotubes, the researchers wear protective equipment, goggles, a mask and gloves. We permit the storage of carbon nanotubes – if at all – only in solution, not as a powder. This prevents them escaping into the air. This is important, since otherwise they can easily enter the body via the lungs by being inhaled and – as researchers report – could even enter the blood.

Pressure stages are installed in the cleanrooms to prevent people and the cleanrooms being contaminated if there is an accident.

Your research group will work at the newly founded Binnig and Rohrer Nanotechnology Center in Rüschlikon. How "research-secure" is it?

Right from the start, we installed the safety pressure stages which we had retrofitted to the ETH Zurich "FIRST" cleanroom laboratory. The nanomaterials room is appropriately secured. We learnt from FIRST and incorporated the knowledge directly into the infrastructure of the research laboratory in Rüschlikon. The safety infrastructure in semiconductor technology cleanrooms has always been at a very high level of development. We are accustomed to working with hazardous gases, i.e. ones that are toxic or flammable. This is why the monitoring sensors are of a very high quality, and the researchers and technologists responsible for operating our laboratories have many years' experience in cleanroom environments.

Are laboratories of this kind also secure relative to the outside world, so nothing can enter the laboratory environment?

Yes. This is ensured by both filters and chemical and physical units known as scrubbers, which clean process gases.

What fascinates you most about this specialist area?

My fascination comes from the technology's unimagined possibilities. The nanoscale area opens up new materials functionalities which we are researching for applications in sensors and which we can then also implement in devices. In our area of research, we have a specific remit to manufacture sensors that are as small and as energy-saving, resource-conserving and cost-efficient as possible. In the Guardian Angels Project, we intend to research technologies for highly energy-efficient systems. The purpose of this is to enable the development of new devices that obtain their energy from the environment, i.e. operate in an energy-autonomous way and can do without battery changes or recharging. In the future, such systems will be even smaller than they are today, and will have functions that we may currently not even be able to predict. We can see meaningful applications to be used in the area of medicine, home care, fast information processing and personal networking as well as in safety and increased energy efficiency in buildings and transport systems.